A reforming apparatus is an apparatus which includes a burner and a reforming-catalyst layer, and which produces a reformed gas (hydrogen-rich gas) containing hydrogen gas from a raw material through a steam reforming process. In the steam reforming process, the raw material, such as kerosene or methane gas, is mixed with water to make a mixture. The mixture is made to flow through the reforming-catalyst layer while the reforming-catalyst layer is heated by the heating gas of the burner. The reformed gas thus produced is used, for example, as a fuel for fuel cells. A conventional example of such reforming apparatus is disclosed in Patent Document 1.
The reforming apparatus disclosed in Patent Document 1 has the following characteristic features.
(1) A raw-fuel vaporizer built in the reforming apparatus vaporizes the raw fuel (raw material).
(2) Multiple reforming pipes, the inside of which is filled with a reforming catalyst, are disposed around the burner, that is, the reforming apparatus is provided with a multi-tubular reforming duct.
(3) A vacuum-insulation container is used for the purpose of thermally insulating the reforming pipes.
(4) The maintenance work for the inside of the apparatus can be carried out only by removing the vacuum-insulation container.
(5) Before the reformed gas that has flowed out from the reforming pipes is made to flow into a low-temperature shift converter, the temperature of the reformed gas is lowered.
(6) There is no device to remove the heat produced by a low-temperature CO-shift catalyst in the low-temperature shift converter and by a CO-removing catalyst in a selective-oxidation CO-remover. The heat is cooled only by the heating gas of the burner.
(7) At the time of heating operation for temperature rising for starting the reforming apparatus, the heating gas of the burner is made to flow inside the vacuum-insulation container without supplying the mixture to the reforming pipes. The low-temperature shift converter and the selective-oxidation CO remover in the vacuum-insulation container are thus heated from their respective outer-circumference sides so as to increase their respective temperatures.(8) The heating gas that has passed by the outer-circumferential side of the selective-oxidation CO remover is directly discharged.
Another conventional example of the reforming apparatus is disclosed in Patent Document 2. The reforming apparatus disclosed in Patent Document 2 is configured to produce a reformed gas by: vaporizing a mixture of a raw material and water (liquid) by a vaporizer provided with a spiral flow passage and the like; and then subjecting the vaporized mixture to a steam reforming process in a reforming portion.    Patent Document 1: JP A-2003-327405    Patent Document 2 JP B-3719931